Issue

The nano revolution

09/01/2008

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The number of products incorporating nanoscale materials is increasing at a rapid rate, but manufacturers are still struggling to find ways to control these materials in the production environment as they ramp up to commercial scale.

By Sarah Fister Gale

In the past few years, the nanotech revolution has gone from great ideas to commercial realization. Manufacturers across multiple industries, from pharmaceuticals and health care to coatings, semiconductors, and microelectronics, are recognizing the current and future impact nanomaterials can have on their products.

Nanomaterials offer great promise for a new generation of products because they deliver higher strength, lower weights, and more easily soluble attributes than have been previously seen in conventional materials.

“Nanotech isn’t a new market or industry–it’s an enabling technology that improves many types of products,” notes Jurron Bradley, senior analyst at Lux Research, a provider of strategic advice and intelligence for emerging technologies, based in New York. “You find it in coatings boosting the efficiency of automobile engines, in nano-enabled finishes protecting electronic devices, and nanoparticulate reformulations that make cholesterol-reducing drugs more effective. These innovations aren’t always visible to consumers, but they improve products and boost margins. That’s why nanomaterials use is only going to keep growing.”

The market has seen recent rapid growth, with great expectations for the near future, says Bradley. In its recently released report, “Nanomaterials State of the Market Q3 2008: Stealth Success, Broad Impact,” Lux estimates that nanotechnology was incorporated into $1.4 trillion worth of products in 2007, up from $497 billion in 2004, representing a compound annual growth rate of 41%. The research firm expects this figure to grow at a compound annual growth rate of 14% through 2015, climbing to $4.0 trillion worth of manufactured goods in that year.

The report notes that established nanotechnology–which includes nanoscale objects and devices based on long-known processes and technologies, such as semiconductor chips with nanometer features and nanoscale particles such as carbon black–dominates the current market, accounting for $1.3 trillion of the $1.4 trillion in nano-enabled manufacturing output in 2007. By 2015, Lux expects emerging nanotech–novel materials currently under development–to take center stage, accounting for $3.1 trillion of the $4.0 trillion in output.

The materials and manufacturing sector saw the greatest impact as nanotech made its way into intermediates like coatings and composites for products like automobiles and buildings; electronics followed at $35 billion from emerging nanotech applications in fields like displays and batteries, while health care trailed with $15 billion in revenue, driven by pharmaceutical applications.

“We are seeing a lot of growth in the electronics and IT sectors,” Bradley says. “Manufacturers still have to prove the technology is viable, but they are seeing much greater acceptance.”

That acceptance is coming after years of trial and error among researchers on how to scale up from the lab to a volume manufacturing facility. From managing human health and safety issues and designing air handling and filtration systems that can manage nanoscale particles, to controlling the way materials are introduced into the environment, processed, and removed, manufacturers are being forced to re-evaluate all of their contamination control processes for the nanoscale.

But is it safe?

A flurry of attention-grabbing research reports and studies warning of the dangers of nanomaterials from special interests groups, such as the Project on Emerging Nanotechnologies and Friends of the Earth, have gained much media attention over the past couple of years, inciting fears among consumers about risky nanomaterials in their products and demanding caution from manufacturers unsure about whether to risk using a product that has potentially or perceived harmful consequences. Even as these materials are proved safe, public perception of risks can have lingering negative effects on marketability, particularly for products sold directly to consumers.

“There is still a lot of concern about nanoparticles,” notes Harry Way, technical director of Netzsch Fine Particle Technologies, a manufacturer of advanced process technology for nanomaterials based in Exton, PA. “In reality, though, we’ve all been exposed to nanoparticles for as long as we’ve been burning things.”

In spite of that statement, the use of nanomaterials in products and the accompanying concerns have made environmental and human health and safety a top priority for standards writers and special interest groups.

A report released in July 2008, “Nanotechnology Oversight: An Agenda for the New Administration,” by former Environmental Protection Agency (EPA) official J. Clarence Davies calls for greater oversight in the use of nanotech materials and defines a roadmap for the next presidential administration that includes immediate and longer-term steps to shore up what he sees as shortcomings of nanotechnology oversight.

Davies calls for the White House and federal agency policymakers to maximize the use of existing laws to improve nanotechnology oversight by defining nanomaterials as “new” substances under federal toxics and food laws, thereby enabling EPA and the Food and Drug Administration (FDA) to consider the novel qualities and effects of nanomaterials. Davies also calls for federal pesticide and workplace safety laws to be used to protect against potential adverse impacts of nanomaterials.

The report highlights the importance of creating sensible nanotechnology policies that will help ensure the safe and sustainable application of nanotechnologies to climate change, food security, water purification, health care, and other pressing global problems.

“The next presidential administration will face a host of complex policy issues concerning energy, the environment, food safety, consumer products, and the workplace,” he writes in the report. “One issue, however, that will impact virtually all of these policy areas is nanotechnology oversight.”

The National Institute for Occupational Safety and Health (NIOSH), the leading federal agency conducting research and providing guidance on the occupational safety and health implications and applications of nanotechnology, is conducting ongoing research into 10 areas of concern that it has identified for safety research regarding the use of nanomaterials. These include toxicity and dosages, fire safety, effectiveness of engineering controls, and safety of current exposure levels.

Meanwhile, many other global organizations are producing their own research and standards documents relating to nanotechnology, including the American National Standards Institute (ANSI), the Institute for Electrical and Electronics Engineers (IEEE), The British Standards Institute (BSI), and the International Organization for Standardization (ISO).

The first steps have been to create standards for measurement, nomenclature, and characterization of nanomaterials, notes Kalman Migler, in the Materials Science and Engineering Laboratory at the National Institute of Standards and Technology (NIST), a non-regulatory federal agency that advances measurement science, standards, and technology, based in Gaithersburg, MD.

“We need to develop reference materials so that we all have the same samples to do the same tests,” he says of the need for standards concerning these issues. “Standards for nano will create immense value by bringing order and efficiency to the marketplace.”

Migler points out that in order to accurately assess the toxicology or characteristics of nanomaterials, the fundamental properties must first be agreed upon. “It creates a uniform approach and develops confidence between buyers and sellers.”

A group within IEEE, a non-profit professional association for the advancement of technology based in Piscataway, NJ, produced IEEE 1650 ??? 2005, one of the first standards for nano to define test methods for measuring electrical properties of carbon nanotubes (CNTs). The standard establishes common metrics and a minimum requirement for reporting.

IEEE chose to focus early on CNTs because there is so much excitement around the commercial applications. Concurrently there have been growing concerns about the safety of CNTs, as some reports suggest they could be dangerous if inhaled.

Classified as single-walled and multi-walled, CNTs are allotropes of carbon with a nanostructure that can have a length-to-diameter ratio greater than 1,000,000–the diameter of a nanotube is on the order of a few nanometers while they can be up to several millimeters in length. They are 20 times as strong as steel, able to bend without breaking, and conduct electricity 1,000 times better than copper, making them excellent candidates for use in displays, integrated circuits, sensors, and other nanoelectronics components.

The standard, which was approved in 2005, was one of the first formal industry efforts to document the minimal amount of information required for reporting lab results for nanotech materials.

More recently, in April 2007, IEEE released its Nanoelectronics Standards Roadmap (NESR), which established a framework for creating standards to help industry transition electronic applications based on nanotechnology from the lab to commercial use. The roadmap recommended the initiation of five nanoelectronic standards: three for nanomaterials involving conductive interconnects, organic sensor structures, and nanodispersions, and two for nanodevices involving nanoscale sensors and nanoscale emitting devices. It also targeted the start of seven nanomaterial standards and five nanodevice standards in 2008.

Under control

While standards bodies are evaluating and defining safety and measurement issues, companies such as Unidym Inc. in Menlo Park, CA, are developing their own internal methods to monitor and control nanomaterials in the manufacturing environment. Unidym manufactures high-purity, electronics-grade CNTs that range from 2 to 5 μm long, using an in-house, fully scalable, and proprietary chemical vapor deposition (CVD) production process.

“The original challenge with carbon nanotubes was availability,” says Glen Irvin, vice president of products, who notes that Unidym has been able to achieve commercial-scale production using a CVD process that involves mixing a carbon-containing gas with a metal-catalyst-coated substrate at a high temperature. The carbon atoms separate from the hydrocarbon gas and attach to the catalyst particles and other carbon atoms to form high-quality nanotubes.

The resulting transparent conductive films are being incorporated into touch films, flat-panel displays, and solar panels. Unidym CNTs are also under development for active and passive components in printed electronics.

The company has perfected methods both to maximize the potential of the CNTs and minimize the contamination risks. Irvin points out that it is equally important to protect humans and the environment from release of the CNTs as it is to keep the CNTs contamination free and contained.

“Over the last nine years we’ve developed unique abilities to create and handle CNTs using automated environments to minimize contamination from operators,” he says, adding that when personnel are in the manufacturing environment, they wear personal protective equipment. “We follow strict guidelines for protection.”

Figure 2. Unidym’s CNTs are used to create end products such as transparent conductive films for touch screens, liquid-crystal displays, and solid-state lighting, as well as specialty inks. Photo courtesy of Unidym Inc.

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Unidym’s CNT products are safely managed with engineering controls such as closed reactor systems, hoods, and mechanical ventilation systems. Key to controlling the material, says Irvin, is processing it in a sealed or closed environment with airflow that is exhausted through a series of HEPA filters out of the building, then suspending it in a dense wet cake or liquid form, which traps the nanotubes to prevent any potential leakage into the environment. Because the CNTs clump together, Irvin points out that they are easily captured in filter systems used in a conventional Class 1000 cleanroom.

In fact, Unidym follows many of the same handling and contamination control management strategies used by the semiconductor industry. This includes comparable fan filter units, air handling systems, and particle monitoring systems to maintain low levels of particulates in the manufacturing environment.

“These thin films are less than 100 nm thick,” Irvin points out. “If a half-micron particle lands on them it’s like it’s been hit with a meteor.”

Irvin is grateful for the work already done by the semiconductor industry on contamination control as it guides much of the work and solutions his team develops for nano. “The semi world is obsessed with controlling particulates, and that’s been a real blessing for us,” he says. “It’s like a gift from our technological forefathers.”

The other unwitting gift Unidym is benefiting from is the surplus of empty cleanroom space in Silicon Valley, just waiting for new occupants. As the semiconductor industry has vacated these high-tech spaces, the nano industry is moving in. “We are tapping into existing cleanroom infrastructure, which means we haven’t had to recreate space.”

Unidym is currently retrofitting cleanroom space in the Silicon Valley area to expand its production operations in the coming months. Irvin notes that the retrofit is fairly simple, involving primarily a change of process flow. The layout and current air handling systems nicely accommodate the company’s needs.

The team will also implement real-time, on-line monitoring of particulates to ensure the robustness of the films manufactured in the environment. Along with identifying contamination events as they occur, Irvin notes that real-time environmental data will be logged for later review in case yield problems arise. “We use scanning electron microscopes to evaluate the films,” he says. “If defects arise, we will be able to go back through the data log to identify or rule out contamination events as the cause.”

Entegris, a provider of materials management products and systems to the microelectronics industry based in Chaska, MN, has also made great strides using CNTs in plastics in place of carbon powders. “Because of their size and how they respond to the polymer molecules for electrostatic dissipation they are a much better choice,” says John Goodman, senior vice president and CTO for Entegris.

He notes that conventional carbon fibers are much larger compared to the polymer molecules, which creates a more loosely held together material. “Abrasions cause those carbon fiber particles to come loose more easily,” he says, “whereas the carbon nanotubes are nearly the same size as the polymer molecules and, when dispersed, they behave similarly to those molecules and are more abrasion resistant. They work well together.”

To maintain control over the CNTs in the manufacturing environment, Entegris receives them in sealed bags that are emptied via ports into gravity-fed, stainless-steel dispersion hoppers with separate air handling systems, ensuring they never have the opportunity to escape into the atmosphere.

Figure 3. Entegris offers several products made with a proprietary blend of CNTs in place of carbon powders in the plastics due to their low off-gassing and abrasion resistance. Shown are a process carrier for hard disk drive manufacturing (left), trays to transport chips during backend processing (center), and a reticle pod for storage and transfer of reticles in the fab (right). Photo courtesy of Entegris.

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The biggest challenge for Entegris in working with CNTs is getting them to disperse in the early process steps. “Nanotubes like to clump together, and if you blend them without dispersing them, the particles tend to agglomerate.”

The large surface area and surface energy of CNTs make their dispersion into liquids difficult. Intermolecular forces increase as particles become smaller, causing cohesive forces in the product. Agglomerates are formed by point-focal or linear cohesive primary particles, while aggregates form by laminar binding.

It took the company years of research to perfect its proprietary dispersion technique, which enables the CNTs to blend with the polymer material to create a uniform material network with the lowest percentage of CNTs possible.

Once the CNTs are dispersed and blended, the mixture is melted and molded into a plastic at which point the CNTs are trapped and cannot be released into the environment.

“The CNTs don’t off-gas; they are very pure,” Goodman notes. “Once the material is blended, off-gassing compared to other raw materials used in cleanrooms is very low. We go to great pains to minimize off-gassing.”

Finding ways to use smaller amounts of nanomaterials and ensuring none of them are lost is key to achieving commercial scale as these materials are very high value, notes Netzsch’s Way. Netzsch’s grinding and dispersion equipment, used to create nanoscale materials, relies on a vacuum transfer of material into liquid where it is transferred to the wet grind process step to maintain control over the matter.

Once the desired nanoscale grind is achieved, the material is either left suspended in liquid or it is coated onto paints, inks, or dried and put into a press to maintain constant control of the materials.

“Grinding is a very clean process,” Way says, noting that other processes that use chemical reactions in producing nanoscale materials can leave chemical residues on the material surface. “It’s more energy efficient, and it results in a very clean material.”

Filter challenges

Not every manufacturer is as far along as Unidym or Entegris in its ability to create and control nanoscale materials at a commercial level, notes Glen Fricano, vice president of business development for Infotonics, a non-profit organization promoting commercial-scale MEMS/NEMS microsystems development, fabrication, and packaging in Canandaigua, NY.

“The biggest challenge a lot of manufacturers face is around filtration systems,” he says. “Existing filtration technology doesn’t stop nanoparticles from getting through. The pore size is simply not small enough.”

This is particularly true of water filtration systems. If nanoparticles of silicon can’t be filtered out, manufacturers face barriers to recycling and disposal of process water, as well as risks to delicate nano-based electronics that can become contaminated by rogue particulates.

Fricano notes that many filter companies are working to develop better filters for nanomaterials that can screen out nano-scale particles.

Entegris, for example, just introduced a filter membrane that features filtration nodes to 5 nm, providing retention of hard particles and gels for advanced processing nodes. The asymmetric ultra-high polyethylene (UPE) membrane design places larger pores upstream in the filter with progressively tighter pores downstream, which lowers the device resistance (pressure drop) to maintain high flow rates for point-of-use and bulk filtration. It is the first 5-nm-rated filter for point-of-use chemical filtration.

However, this is only one solution, and Fricano notes that many filtration companies have struggled in creating nanoscale filters that don’t slough off additional contaminants and can maintain flow and pressure rates through extremely small pore sizes.

“You never solve the problem completely; you just get better at it,” Fricano says. “At some point, you’ve just got to shoot the engineer, go into production, and just keep working to make the system better.”

He estimates it can take 6 to 24 months to successfully address nanoscale contamination control problems in the manufacturing environment, adding that the solutions often result in new problems down the line.

He also points out that the ongoing improvement process is an added expense companies need to factor into their manufacturing costs. “If you’ve got a team of people constantly trying to improve the process, it costs money,” he says. “You always need to think about the downstream ramifications of what you are doing.”

Looking ahead

In the next few years, nanomaterials will become commonplace in cleanroom operations, leaving manufacturers to figure out the best strategies for handling them in ways that control costs and manage yields.

New standards and guidance from government agencies will help to guide this process, but in the meantime, suggests Unidym’s Irvin, companies can benefit from partnering with industry experts and learning lessons from existing cleanroom operations.

“Contamination control has been on our minds since the beginning of working with nanomaterials,” Irvin says. “We knew we’d be in a Class 100 cleanroom or better, and we look to the semi industry daily. They paved the way for what we are doing today.”